doc/admin-guide/plugins/xdebug.en.rst - trafficserver - Git at Google

 .. Licensed to the Apache Software Foundation (ASF) under one
    or more contributor license agreements.  See the NOTICE file
    distributed with this work for additional information
    regarding copyright ownership.  The ASF licenses this file
    to you under the Apache License, Version 2.0 (the
    "License"); you may not use this file except in compliance
    with the License.  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing,
    software distributed under the License is distributed on an
    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    KIND, either express or implied.  See the License for the
    specific language governing permissions and limitations
    under the License.

 .. include:: ../../common.defs

 .. default-domain:: cpp

 .. _admin-plugins-xdebug:

 XDebug Plugin
 *************

 The `XDebug` plugin allows HTTP clients to debug the operation of
 the Traffic Server cache using the default ``X-Debug`` header. The plugin
 is triggered by the presence of the ``X-Debug`` or the configured header in
 the client request. The contents of this header should be the names of the
 debug headers that are desired in the response. The `XDebug` plugin
 will inject the desired headers into the client response.  In addition, a value of the
 form ``fwd=n`` may appear in the ``X-Debug`` header, where ``n`` is a nonnegative
 number.  If ``n`` is zero, the ``X-Debug`` header will be deleted.  Otherwise, ``n`` is
 decremented by 1.  ``=n`` may be omitted, in which case the ``X-Debug`` header will
 not be modified or deleted.

 `XDebug` is a global plugin. It is installed by adding it to the
 :file:`plugin.config` file. It currently takes a single, optional
 configuration option, ``--header``. E.g.

 ::

     --header=ATS-My-Debug

 This overrides the default ``X-Debug`` header name.

 All the debug headers are disabled by default, and you need to enable them
 selectively by passing header names to ``--enable`` option.

 ::

     --enable=x-remap,x-cache

 This enables ``X-Remap`` and ``X-Cache``. If a client's request has
 ``X-Debug: x-remap, x-cache, probe``, XDebug will only inject ``X-Remap`` and
 ``X-Cache``.

 To enable the JSON transaction header probe functionality:

 ::

     --enable=probe-full-json

 This allows clients to request ``X-Debug: probe-full-json`` to receive request
 and response header information in a structured JSON format.


 Debugging Headers
 =================

 The `XDebug` plugin is able to generate the following debugging headers:

 Via
     If the ``Via`` header is requested, the `XDebug` plugin sets the
     :ts:cv:`proxy.config.http.insert_response_via_str` configuration variable
     to ``3`` for the request.

 Diags
     If the ``Diags`` header is requested, the `XDebug` plugin enables the
     transaction specific diagnostics for the transaction. This also requires
     that :ts:cv:`proxy.config.diags.debug.enabled` is set to ``1``.

 Probe
     All request and response headers are written to the response body. Because
     the body is altered, it disables writing to cache. Further, the ``Content-Type``
     value is modified to ``application/json`` and an ``X-Original-Content-Type``
     response header is added to indicate the original response ``Content-Type``
     value.

     In conjunction with the `fwd` tag, the response body will contain a
     chronological log of all headers for all transactions used for this
     response.

     Layout:

     - Request Headers from Client  -> Proxy A
     - Request Headers from Proxy A -> Proxy B
     - Original content body
     - Response Headers from Proxy B -> Proxy A
     - Response Headers from Proxy A -> Client

 Probe-Full-JSON
     Similar to `Probe` but formats the output as a complete JSON object
     containing request and response headers. The response body is modified to
     include client request headers, proxy request headers, the original server
     response body, server response headers, and proxy response headers in a
     structured JSON format. In contrast to Probe, the response content with
     this feature is parsable with JSON parsing tools like ``jq``. Because the
     body is altered, it disables writing to cache and changes the Content-Type
     to ``application/json``.  However, as with the ``probe`` header, a
     ``X-Original-Content-Type`` response header is added to indicate the original
     response ``Content-Type`` value.

     JSON Nodes:

     - ``client-request``: Headers from the client to the proxy.
     - ``proxy-request``: Headers from the proxy to the origin server (if applicable).
     - ``server-body``: The original response body content from the origin server.
     - ``server-response``: Headers from the origin server to the proxy.
     - ``proxy-response``: Headers from the proxy to the client.

     For the ``server-body`` value, by default the plugin chooses an encoding
     based on the original response ``Content-Type``:

       - Textual content types (e.g. ``text/*``, and types containing ``json``,
         ``xml``, ``html``, ``csv``, or ``javascript``) are JSON-escaped.
       - Other content types are hex-encoded.

     You can override the derived encoding by providing an option with the
     ``probe-full-json`` header value:

       - ``X-Debug: probe-full-json=escape`` forces JSON escaping of the origin body.
       - ``X-Debug: probe-full-json=hex`` forces hex encoding of the origin body.
       - ``X-Debug: probe-full-json=nobody`` omits the origin body entirely.


     Here's an example of the JSON output::

         $ curl -s -H"uuid: 1" -H "Host: example.com" -H "X-Debug: probe-full-json" http://127.0.0.1:61003/test | jq
         {
             "client-request": {
                 "start-line": "GET http://127.0.0.1:61000/test HTTP/1.1",
                 "uuid": "1",
                 "host": "127.0.0.1:61000",
                 "x-request": "from-client"
             },
             "proxy-request": {
                 "start-line": "GET /test HTTP/1.1",
                 "uuid": "1",
                 "host": "127.0.0.1:61000",
                 "x-request": "from-client",
                 "Client-ip": "127.0.0.1",
                 "X-Forwarded-For": "127.0.0.1",
                 "Via": "http/1.1 traffic_server[f47ffc16-0a20-441e-b17d-6e3cb044e025] (ApacheTrafficServer/10.2.0)"
             },
             "server-body": "Original server response",
             "server-response": {
                 "start-line": "HTTP/1.1 200 ",
                 "content-type": "text/html",
                 "content-length": "24",
                 "x-response": "from-origin",
                 "Date": "Tue, 19 Aug 2025 15:02:07 GMT"
             },
             "proxy-response": {
                 "start-line": "HTTP/1.1 200 OK",
                 "content-type": "application/json",
                 "x-response": "from-origin",
                 "Date": "Tue, 19 Aug 2025 15:02:07 GMT",
                 "Age": "0",
                 "Transfer-Encoding": "chunked",
                 "Connection": "keep-alive",
                 "Server": "ATS/10.2.0",
                 "X-Original-Content-Type": "text/html"
             }
         }

 X-Cache-Key
     The ``X-Cache-Key`` header contains the URL that identifies the HTTP object in the
     Traffic Server cache. This header is particularly useful if a custom cache
     key is being used.

 X-Cache
     The ``X-Cache`` header contains the results of any cache lookups.

     ==========  ===========
     Value       Description
     ==========  ===========
     none        No cache lookup was attempted.
     miss        The object was not found in the cache.
     hit-stale   The object was found in the cache, but it was stale.
     hit-fresh   The object was fresh in the cache.
     skipped     The cache lookup was skipped.
     ==========  ===========

     If a request goes through multiple proxies, each one appends its X-Cache header content
     the end of the existing X-Cache header. This is the same order as for the
     ``Via`` header.

 X-Cache-Generation
   The cache generation ID for this transaction, as specified by the
   :ts:cv:`proxy.config.http.cache.generation` configuration variable.

 X-Milestones
     The ``X-Milestones`` header contains detailed information about
     how long the transaction took to traverse portions of the HTTP
     state machine. The timing information is obtained from the
     :func:`TSHttpTxnMilestoneGet` API. Each milestone value is a
     fractional number of seconds since the beginning of the
     transaction.

 X-Transaction-ID
     A unique transaction ID, which identifies this request / transaction. This
     matches the log field format that is also available, %<cruuid>.

 X-Remap
     If the URL was remapped for a request, this header gives the *to* and *from* field from the line in remap.config that caused
     the URL to be remapped.

 X-Effective-URL
     If the URL was remapped for a request, this header gives the URL resulting from the remapping. Note that if there are
     multiple remaps, this header aggregates the URLs, space-comma-separated. The URLs are inside doublequotes.

 X-ParentSelection-Key
     The ``X-ParentSelection-Key`` header contains the URL that is used to
     determine parent selection for an object in the Traffic Server. This
     header is particularly useful if a custom parent selection key is
     being used.
	.. Licensed to the Apache Software Foundation (ASF) under one
	or more contributor license agreements. See the NOTICE file
	distributed with this work for additional information
	regarding copyright ownership. The ASF licenses this file
	to you under the Apache License, Version 2.0 (the
	"License"); you may not use this file except in compliance
	with the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing,
	software distributed under the License is distributed on an
	"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	KIND, either express or implied. See the License for the
	specific language governing permissions and limitations
	under the License.

	.. include:: ../../common.defs

	.. default-domain:: cpp

	.. _admin-plugins-xdebug:

	XDebug Plugin
	*************

	The `XDebug` plugin allows HTTP clients to debug the operation of
	the Traffic Server cache using the default ``X-Debug`` header. The plugin
	is triggered by the presence of the ``X-Debug`` or the configured header in
	the client request. The contents of this header should be the names of the
	debug headers that are desired in the response. The `XDebug` plugin
	will inject the desired headers into the client response. In addition, a value of the
	form ``fwd=n`` may appear in the ``X-Debug`` header, where ``n`` is a nonnegative
	number. If ``n`` is zero, the ``X-Debug`` header will be deleted. Otherwise, ``n`` is
	decremented by 1. ``=n`` may be omitted, in which case the ``X-Debug`` header will
	not be modified or deleted.

	`XDebug` is a global plugin. It is installed by adding it to the
	:file:`plugin.config` file. It currently takes a single, optional
	configuration option, ``--header``. E.g.

	::

	--header=ATS-My-Debug

	This overrides the default ``X-Debug`` header name.

	All the debug headers are disabled by default, and you need to enable them
	selectively by passing header names to ``--enable`` option.

	::

	--enable=x-remap,x-cache

	This enables ``X-Remap`` and ``X-Cache``. If a client's request has
	``X-Debug: x-remap, x-cache, probe``, XDebug will only inject ``X-Remap`` and
	``X-Cache``.

	To enable the JSON transaction header probe functionality:

	::

	--enable=probe-full-json

	This allows clients to request ``X-Debug: probe-full-json`` to receive request
	and response header information in a structured JSON format.


	Debugging Headers
	=================

	The `XDebug` plugin is able to generate the following debugging headers:

	Via
	If the ``Via`` header is requested, the `XDebug` plugin sets the
	:ts:cv:`proxy.config.http.insert_response_via_str` configuration variable
	to ``3`` for the request.

	Diags
	If the ``Diags`` header is requested, the `XDebug` plugin enables the
	transaction specific diagnostics for the transaction. This also requires
	that :ts:cv:`proxy.config.diags.debug.enabled` is set to ``1``.

	Probe
	All request and response headers are written to the response body. Because
	the body is altered, it disables writing to cache. Further, the ``Content-Type``
	value is modified to ``application/json`` and an ``X-Original-Content-Type``
	response header is added to indicate the original response ``Content-Type``
	value.

	In conjunction with the `fwd` tag, the response body will contain a
	chronological log of all headers for all transactions used for this
	response.

	Layout:

	- Request Headers from Client -> Proxy A
	- Request Headers from Proxy A -> Proxy B
	- Original content body
	- Response Headers from Proxy B -> Proxy A
	- Response Headers from Proxy A -> Client

	Probe-Full-JSON
	Similar to `Probe` but formats the output as a complete JSON object
	containing request and response headers. The response body is modified to
	include client request headers, proxy request headers, the original server
	response body, server response headers, and proxy response headers in a
	structured JSON format. In contrast to Probe, the response content with
	this feature is parsable with JSON parsing tools like ``jq``. Because the
	body is altered, it disables writing to cache and changes the Content-Type
	to ``application/json``. However, as with the ``probe`` header, a
	``X-Original-Content-Type`` response header is added to indicate the original
	response ``Content-Type`` value.

	JSON Nodes:

	- ``client-request``: Headers from the client to the proxy.
	- ``proxy-request``: Headers from the proxy to the origin server (if applicable).
	- ``server-body``: The original response body content from the origin server.
	- ``server-response``: Headers from the origin server to the proxy.
	- ``proxy-response``: Headers from the proxy to the client.

	For the ``server-body`` value, by default the plugin chooses an encoding
	based on the original response ``Content-Type``:

	- Textual content types (e.g. ``text/*``, and types containing ``json``,
	``xml``, ``html``, ``csv``, or ``javascript``) are JSON-escaped.
	- Other content types are hex-encoded.

	You can override the derived encoding by providing an option with the
	``probe-full-json`` header value:

	- ``X-Debug: probe-full-json=escape`` forces JSON escaping of the origin body.
	- ``X-Debug: probe-full-json=hex`` forces hex encoding of the origin body.
	- ``X-Debug: probe-full-json=nobody`` omits the origin body entirely.


	Here's an example of the JSON output::

	$ curl -s -H"uuid: 1" -H "Host: example.com" -H "X-Debug: probe-full-json" http://127.0.0.1:61003/test \| jq
	{
	"client-request": {
	"start-line": "GET http://127.0.0.1:61000/test HTTP/1.1",
	"uuid": "1",
	"host": "127.0.0.1:61000",
	"x-request": "from-client"
	},
	"proxy-request": {
	"start-line": "GET /test HTTP/1.1",
	"uuid": "1",
	"host": "127.0.0.1:61000",
	"x-request": "from-client",
	"Client-ip": "127.0.0.1",
	"X-Forwarded-For": "127.0.0.1",
	"Via": "http/1.1 traffic_server[f47ffc16-0a20-441e-b17d-6e3cb044e025] (ApacheTrafficServer/10.2.0)"
	},
	"server-body": "Original server response",
	"server-response": {
	"start-line": "HTTP/1.1 200 ",
	"content-type": "text/html",
	"content-length": "24",
	"x-response": "from-origin",
	"Date": "Tue, 19 Aug 2025 15:02:07 GMT"
	},
	"proxy-response": {
	"start-line": "HTTP/1.1 200 OK",
	"content-type": "application/json",
	"x-response": "from-origin",
	"Date": "Tue, 19 Aug 2025 15:02:07 GMT",
	"Age": "0",
	"Transfer-Encoding": "chunked",
	"Connection": "keep-alive",
	"Server": "ATS/10.2.0",
	"X-Original-Content-Type": "text/html"
	}
	}

	X-Cache-Key
	The ``X-Cache-Key`` header contains the URL that identifies the HTTP object in the
	Traffic Server cache. This header is particularly useful if a custom cache
	key is being used.

	X-Cache
	The ``X-Cache`` header contains the results of any cache lookups.

	========== ===========
	Value Description
	========== ===========
	none No cache lookup was attempted.
	miss The object was not found in the cache.
	hit-stale The object was found in the cache, but it was stale.
	hit-fresh The object was fresh in the cache.
	skipped The cache lookup was skipped.
	========== ===========

	If a request goes through multiple proxies, each one appends its X-Cache header content
	the end of the existing X-Cache header. This is the same order as for the
	``Via`` header.

	X-Cache-Generation
	The cache generation ID for this transaction, as specified by the
	:ts:cv:`proxy.config.http.cache.generation` configuration variable.

	X-Milestones
	The ``X-Milestones`` header contains detailed information about
	how long the transaction took to traverse portions of the HTTP
	state machine. The timing information is obtained from the
	:func:`TSHttpTxnMilestoneGet` API. Each milestone value is a
	fractional number of seconds since the beginning of the
	transaction.

	X-Transaction-ID
	A unique transaction ID, which identifies this request / transaction. This
	matches the log field format that is also available, %<cruuid>.

	X-Remap
	If the URL was remapped for a request, this header gives the to and from field from the line in remap.config that caused
	the URL to be remapped.

	X-Effective-URL
	If the URL was remapped for a request, this header gives the URL resulting from the remapping. Note that if there are
	multiple remaps, this header aggregates the URLs, space-comma-separated. The URLs are inside doublequotes.

	X-ParentSelection-Key
	The ``X-ParentSelection-Key`` header contains the URL that is used to
	determine parent selection for an object in the Traffic Server. This
	header is particularly useful if a custom parent selection key is
	being used.